As I wrote, it can be complicated. I was on T3(Cytomel) from 1994 until 2005, when it appeared to stop working. Before that, I felt great, including restoration of erections. I was under the care of an endocrinologist who really didn't make any effort to figure what might be going on. Suddenly becoming refractory to thyroid medication coincided with my relapse into bipolar illness, which was/is treatment resistant. 17 years on a long, frustrating journey to restore my health and function. That's why I say, keep at it and read all the research. It might give you a clue as to what's going on.As I indicated in my post, I have already experimented with every possible combination, including adding T3 in various doses, over the last 10+ years. The only instance in that time frame I sufficiently suppressed was when I took T4 alone, go figure, but I wasn't able to maintain it for whatever reason. The only part of this that has me thinking why the TSH hasn't suppressed is a problem with the pituitary or hypothalamus, but if so, then the treatment is to increase the dose of thyroid replacement. T3 monotherapy works for some, but was ineffective in my case and made me feel worse, stresses the heart/adrenals, etc. in the long run. Since this post, I have increased the dose of NP Thyroid to 105mg and will retest. I also will be switching to compounded NDT which is a purer product to see if I get any better results on that. Failing that, experimenting with T4 only or T4 added to the NDT will be next.